Temperature alarm systems



July 10, 1962 E. w. J. EVERETT ETAL 3,044,049

TEMPERATURE ALARM SYSTEMS Filed 001;. 4, 1957 I MR2 E1 31" 1 FIG.1.

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Fxwfrf 14/4172? fan 5r 19066367 INVENTORS.

W ATTORNEYS.

' conditions such as fire will heat the exposed junctions 3,944,049 Patented July 10, 1962 hired rates patent re contacts which are regarded as essential for automatic resetting.

Further in accordance with the present invention fire warning apparatus employing a sensitive two-coil relay, such as e.g. described in the aforesaid patent embodying two contacts engaged individually by a contact movable in reference to a signal to engage one of the said two contacts to make the warning circuit and returned into engagement with the other of the said two contacts when said signal ends so as automatically to reset the apparatus,

is characterised in that means is provided which, following automatic resetting of the apparatus separates and ture in, or in the vicinity of, a power unit or other unit maintains constantly separated pending the introduction susceptible to variations in temperature and is, for exof a signal to bring the apparatus into operation, the conample, useful in aircraft for giving a Warning to the pilot tacts of he s nsitive two-coil relay. In eitect this amounts or crew in the event of fire or an abnormal rise in temt0 locating the moving Contact which responds to the Said peraure occurring. In Patent No, 2,589,869 there is signal in a normal position which is clear of either of the proposed electrically perated appapatus f bringing into two contacts with which such moving contact cooperates operation, by reason of a sudden increase of temperature in the g g into and out of operation the Warning at a control source, a warning or other electrically m nsactuated device, and which comprises a very sensitive relay The af r said positioning and maintenance of the movoperable by a low EMF. an electrically operated Warning contact into a normal free or entirely oit position ing or other electrically operated device operated from has the advantage that substantial weight is saved as a source of electrical energy having a much greater outspecial condensers to suppress radio interference are now put than said low E.M.F. a holding circuit for the said llhtlooossaty, vand, a150 arising therefrom ipi g 0f the device, normally inoperative means controlled by the contacts to maintain them clean is now only effected actuation of said relay to connect said electrically operated during e ry S t periods When the moving cont-act Warning or other device efiect-ively to the said higher is in engagement with either of the fixed Contacts thereby source whilst transferring the electrical load from obviating the hooessity of e p l ing relay or self intersaid relay to said holding circuit, a test circuit with means p g Circuits f r Pr ing the intermittent making to bring it selectively into operation, and means adapted d r aking of the said movable contact and one of the upon bringing in the test circuit to introduce into the cir- Said other ta ts. cuit of the said low producing means, an Still further in accordance with the present invention substantially equal to the operative output of the said pp s for giving a signal of a Sudden change in ternlatter circuit perature in, or in the vicinity of, a power unit or other F h purpose f bt i i th id 1 t apparatus comprises a sensitive two-coil relay having one initiate the operation of the warning apparatus it is premovable Contact otlgagoahto With e f tW other conferred to distribute in known manner thermo-couples taots depending on direction of the Current flowing about h power i t a l lit f l bl paints, through the coils, a first coil of the two-coils of the relay uch thermo-c0uples being cgnnected to. a singla Warning belng connected to a control force, the circuit is apparatu and being adapted on actuatign either inde- PIOV'ldEd through the Oth$I', l.. the second COl]. Of the pendently of each other or collectively, to develop the relay and Which circuit is t1 normal inoperative Warning low EMF, designed to initiate the operation of the elecohfoutt op to he made operative on engagement of trically operated warning apparatus as soon as there is a Sold movlhg Contact With the pp p one f Said distinct sudden rise in temperature as opposed to a smooth o other contacts ohd held independently of Said l, progressive rise at or below the predetermined rate. Thus this latte! of Wanting circuit including elootfioally it was suggested that a plurality of thermo-couples should ohotgis ed moons energised as the result @of the Closing of be connected in series and that each thermo-couple should Such olroutt Serving bring into Position ready for have one junction exposed to the immediate ambient teni- 5O engagement y the moving Contact of he sensitive twoperature conditions but that the other junction should be coll relay the other of Said tWO other Contacts Which, slightly shielded from such ambient temperature. This When engaged y the movable oohtaot, Shorts t the results in a slow rate of temperatur increase heating Warning oh'otltt thereby also do-ohelgisthg the Said both junctions simultaneously so that there is no means Yotumihg tho cohtttot displace/able y the Said developed whereas a sudden increase due to abnormal means to on idle or Position clear f e said movable contact. Movable designates the contact which is actuated in receiving a warning signal.

h f o the foregoing i will b appreciated that Embodiments of the invention are illustrated by the in Patent No. 2,589,869 a number of relays produce a acFOmPanYmg drawings in Which FIGURE 1 s 8 Cirpulsing circuit to obviate the objections aforesaid. Howcult dlagtam -h ever, arising from further experiments We have now FIGURE 2 illustrates a suitable form of miniature troduced an apparatus for giving a signal for the purpo Solenoid for actuating the displaceable one of the two mentioned which, whilst being appropriate to automatic contacts Whlch aro engaged by Swinging oohtaot 0f resetting, obviates during normal conditions of the appathe aforosaid Sehsttlvo o F yratus the necessity of relying on continuous wiping 01 Referring to the circuit illustrated in FIGURE 1, a regular making and breaking of the contacts of the sensicontrol Source Whlch conveniently comprises a P tive relay whilst employing two contacts alternately en- Tahty of thofmo-ootlples, hlttodlloes the y low gaged b h ta t whi h i displaced f bringing th which initiates the operation of the apparatus for bringing apparatus into and out of operation and in pursuance in a Warning signal and immediately following such thereof according to the present invention electrically initiation the warning signal is maintained on by means operated means is provided by which the latter mentioned which is energised from a normal source, eg. a 24 volt contact is normally maintained clear of the two fixed source as used in aircraft, the negative and positive leads 3,44,49 TEMPERATURE ALARM SYTEMS Ernest Walter James Everett, Withdean, Brighton, and Robert George Gilbert, Worthing, England, assignors to Speed Developments Company Limited, Marine Works, Hove, Sussex, England Filed Oct. 4, 1957, Ser. No. 638,24 Claims priority, application Great Britain May 1, 1957 6 Claims. (Cl. 340-227) This invention relates to apparatus for giving a signal When there is a sudden high rate of change in temperamore rapidly and thus produce an EMF.

access-s of which are indicated by the reference numerals 1 and 2 respectively. The control source CS is connected across the operating coil MR1 of the sensitive two-coil miniature relay which is adapted to operate for very low E.M.F., i.e. a few millivolts through a test button T normally closing contacts 19 and 21 so that at this condition the test button is in parallel with a low resistance R1 (conveniently 1 ohm), in series with the control source CS and the relay coil MR1 which is the initiating or first operating coil of a miniature relay designed to respond to the few millivolts received from the control source CS, the other coil of this miniature relay being indicated by the reference MR2. The moving contact of this miniature relay is indicated by the reference numeral 16. The miniature relay is thus desirably similar in construction to that normally associated with delicate galvanometers,

that is to say in which the direction of the current flows through the relay cells has an ettect upon the direction in pressure to alternately lcnock-on and knocleofii the movin Contact as hereinafter expl 1. Tb

Contact 2023123 51; norr n lly being spa d from fife Contact 10 and held stationary, is moved into a position ready for engagement by the contact 11 when the warning on condition occurs, so that the only period of make between contacts 10 and is a momentary one occurring at the ending of the warning-on condition by reason of such making of contacts 10 and 20 shorting out a master relay which serves to maintain the warning-on condition. The said master relay is indicated by the reference letter M.

It will be seen that the master relay M is connected from the main negative supply lead 1 to the miniature relay coil MR2 through a return hairspring 13 to the moving contact 10. The fixed contact 12 is connected through a resistor R3 (approximately ohms) and a condenser C (which may be 140 ,uf.) to the main positive lead 2, and for the displacement of the contact 20 a miniature relay or solenoid shown by Way of example as a solenoid S (having a value of about 200 ohms) is included in the miniature or millivolt relay. The main relay M operates normally open contacts 17 in a lead 11 to connect the solenoid S via a lead 3 and a resistor R4 to the positive lead 2, the other side of the solenoid S being connected tonegative via lead 9 so that when a signal from source CS closes the contacts 10 and 12 and thereby connects the master relay M to the positive lead 2 through resistor R3 and condenser C, the main relay coil M is energised so as to close contacts 17 thereby energising solenoid S and also transferring the holding current for the relay M via the contacts 17 lead 14, resistor R2, (about 800 ohms) and lead 4. Hence the miniature relay coil MR2 is promptly relieved of the load due to the higher source and the resistor R2 now carries this holding current. The contact 17 also serves to join the positive lead 2 via the lead 11 to a warning lamp 18 or other suitable device to energise it.

A further contact 15 is also operated by the master relay coil M and when operated consequent upon energising of the relay M joins the fixed contact 12, via the resistor R3, lead 6 to the main negative lead 1 through a resistor R7 (about 1,500 ohms) to provide a knock-off current between contacts and 12 after Warning operation to prevent sticking of the contacts. The normally closed condition of the change-over contact 15 (i.e. that shown in FIGURE 1), i.e. when in the position when the apparatus is not operating the Warning device 18, serves to join the condenser C, via leads 5, 6 and 7 across a resistor R6 (4-00 ohms) to ensure that the condenser C will be fully discharged in order to allow maximum displacement current to flow through itself when required on operation.

The reset or bottom contact 26 of the millivolt relay is attached to the plunger of the solenoid S and also via the lead 9 to the main negative lead 1. it is therefore apparent that when master relay M has operated and the reset contact an is displaced by operation of the solenoid S, then upon the moving contact in engaging contact 20 due to a reduction in cutyut from acute CS knock-on between contacts 10 and. 20 until the master relay The rr i z iin neg coil MR2 of the millivolt relay, the hairspring 13, the moving contact 10, the fixed contact 12, the resistor R3, the lead 5, and the condenser C to the main positive lead 2.

This displacement charging current through the condenser C is in such a direction through coil MR2 as to cause an implementing pressure which may be termed a knock-on pressure between contacts 10 and 12 thus ensuring such a low contact resistance as to obviate sparking across the contacts, and master relay M is energised. Relay M operates its contact 17 in the lead 11 which provides a holding circuit, removing the load from the millivolt relay contacts 11? and 12 as follows:

The main negative lead 1, the relay coil M, the lead 14, the resistor R2, the lead 4, the contact 17 and the lead 11 to the main positive lead 2.

At the same time, the movable or armature member of the contact 15 is operated, thus reversing the direction of current through the coil MR2, i.e. providing a knockofi current through coil MR2 to separate the contacts 10 and 12 of the millivolt relay. The circuit for this knock-01f current is as follows:

The main negative lead 1, the resistor R7, the con tact 15, the lead 6, the resistor R3, the fixed contact 12, the moving contact 10, the hair spring 13, the coil MR2, the lead 14, the resistor R2, the lead 4, the contact 17, and the lead 11 to the main positive lead 2. This reversal of the direction of current through the coil MR2 moves the contact 10 away from the contact 12, which momentarily breaks the circuit for this current until, under the influence of the high output from the source CS they are moved together again to remake the circuit. Thus, contacts 10 and 12 make and break continually to ensure that such contacts are readily freed from during the operation of the warning device 18 without shorting out the master relay M and contacting when the output from the source CS is reduced. That is to say as there is intermittent operation of the contact 16) into and out of engagement with the contact 12 while the warning device is on it is not possible for the contacts 16 and 12 to tend to stick together and accordingly immediately the output from the source CS drops due to the extinguishing of a fire outbreak the contact will on its movement away from the contact 12, not return into engagernent with the contact 12 but will engage or stop against the contact 20 which will have been displaced to a position for being engaged by the returning contact 10 as hereinafter explained.

Upon the closing of the contact 17 when the relay M is energised, two further circuits are completed, one for the warning lamp 18 from the main positive lead 2, the lead 11, the contact 17, and the lamp 18 to the main negative lead 1, and the other for energising the miniature solenoid S as follows:

The main positive lead 2, the lead 11, the contact 17, the lead 4, the lead 3, the resistor R4, the solenoid coil S, and the lead 9 to the main negative lead 1.

The solenoid S is thus energised, displacing the reset contact 20 into the return path of the movable contact 10 which is still in intermittent contact with the fixed contact 12 due to the high output from source CS. It will be seen that the contact 10 whilst it makes intermittent engagement with the contact 12, cannot engage with the contact 29 during the operation of the warning device, so that the contact 10 moves into engagement with the contact 20 upon reduction in the output of the source CS, hereby ensuring immediately upon touching of the contacts 10 and 20 that the engagement of the contacts 10 and 20 is assisted by the influence of an implementing pressure or knock-on current which will flow through the coil MR2 now in series with the contact 20 due to the shorting of the master relay M, this again obviating erratic engagement of the contacts and obviating sparking. The relay M now being de-energised, opens contacts 15 and 17 which subsequently de-energise solenoid S so that the contact 24) is now returned to its normal position completely free of the contact 10. This has a wiping effect between the contacts which prevents accumulation of foreign matter between the engaging faces of the contacts.

The latter described operation ensures a very positive action, and the breaking of the holding contact 17 with consequent de-energising of the solenoid S and displacement of the contact 20 into the neutral position, whereby the moving contact it) is free to float without contacting the contacts 12 and 29. The making of the contacts 10 and 2t and their subsequent breaking produces a good wiping action to free the contacts of foreign particles, this wiping being most eifective due to the tendency of the contact 10 to follow for a short distance of travel the relatively retreating contact 20.

The test button T is provided for testing the apparatus at any time. This button is adapted to connect the resistor R1 to negative lead 1 through relay M via lead 8, and positive lead 2 through a resistor R5 (800 ohms) and lead 27, the resistor R1 being normally short circuited by the fixed contacts 19 and 21 of the test button and in series with the control source CS tocoil MR1.

The operation of the test button T is as follows: Normally'it bridges the contacts 19 and 21 to short a resistance R1 of about 1 ohm and when making .a test the button is depressed to bridge a pair of contacts 24 and 25 to connect the main positive line 2 through a resistance R5 of conveniently about 800 ohms to one side of the resistance R1 via lead 26 and one side of the coil MR1. At the same time, the other side of resistor R1 and one side of the control source CS are connected via lead 16, contacts 22, 23 of T, through lead 8 and relay M to the negative lead 1. This results in applying a very low across the coil MRI, which will initiate operation of the warning device.

The miniature solenoid S is illustrated in FIGURE 2 and comprises the usual coil S in which is located the usual axially displaceable core S carrying at one end the contact 20, its other end receiving the inner end of an involute hair spring 13 the other end of which is secured to the end plate or casing of the solenoid and also can receive the lead 9. Behind the solenoid is shown the moving contact 19 and the fixed contact 12, the free end of the moving contact 10 being bent or shaped to ensure it engaging the other two contacts. The casing of the sensitive relay containing the contacts 10, 12 and Zil is indicated at 28.

We claim:

1. In apparatus for giving a warning when there is a sudden high rate of change in temperature, e.g. such as occurs at the outbreak of a fire, which is detected by means responsive to such form of change to produce a low signal, a very sensitive relay operable by said signal; an electrically actuated Warning member: a holding circuit operable from a source of much greater than the said signal of low produced by said means and brought in by said very sensitive relay when such relay is actuated by said signal, means with said holding circuit to bring in said Warning member, said holding circuit when closed taking the electrical load for keeping in said warning member independently of said relay, said very sensitive relay having first and second contacts and a moving contact normally separated from said first and second contacts and actuated by the said low E.M.F. signal to engage the said first contact to bring in the said holding circuit, said second contact when engaged by the moving contact cutting out the said signal producing means; means producing a knock-on implementing pressure between said moving contact and said first contact when the moving contact and said first contact engage an implementary operating when the holding circuit is in to produce an implementing knock-off current to said first contact during the continuance of said signal to make and break said moving and first contacts intermittently, said second contact normally being held out of the path or" movement of said moving contact, electrically energised means adapted to bring said second contact into said path of movement when the holding circuit is closed to position the said second contact for engagement by the moving contact When the output producing said low signal is reduced and to return said second contact to a normal position out of said path of movement when the holding circuit is broken.

2. Apparatus for giving a warning when there is a sudden high rate of change in temperature, e.g. such as occurs at the outbreak of a fire, comprising means responsive to such form of change to produce a low signal, a very sensitive relay operable by said signal and incorporating a relay coil energised from said lowBh/LF. signal and a relay switching coil; a normally cut-out holding circuit served from a source of much greater than the said signal of low produced by said means and brought in by said very sensitive relay when such relay is actuated by said signal, a warning appliance, said very sensitive relay having first and second contacts and a moving contact with resilient means which normally maintains the moving contact separated from said two contacts and also having two separately energised coils to actuate the said moving contact, a normal electrical connection between said low E.M.F. signal producing means and one of said coils to actuate the moving contact by the said low signal to engage the moving contact with said first contact to bring in the said holding circuit and subsequently to engage the said second contact to cut out said holding circuit and restore the apparatus to its normal condition, and electrically energised means to produce relative displacement of the said second contact with respect to said moving contact, said second contact normally being held by said electrically energised means out or" the path of movement of said moving contact; a master relay in said holding circuit so as to be energisable from but normally isolated from said greater source and connectable to said greater source via said moving contact and said first contact; contact means closed and opened by the energising and de-energising of said master relay and when closed bringing in said electrically energised means and said holding circuit and warning appliance when the said low E.M.F. signal is put out by said low source to displace said second contact into the path of free movement of said movable contact, so as to be engaged by the said movable contact when the said 10W output is reduced, means to supply implementary knock-on current charge to said relay switching coil when said master relay is brought into circuit to implement the pressure of the moving contact against said first contact and when said signal disappears to produce a momentary knock-on action between said moving contact and said second contact and the shorting of said master relay and de-energising of said electrically energised means to restore the apparatus to normal condition.

3. Apparatus for giving a signal of a sudden high rate of change of temperature, eg such as occurs on the outbreak of fire at a control source, comprising thermocouple means adapted to produce a low voltage signal consequent upon a sudden rise in temperature at said source; a first circuit including and deriving low voltage current from said thermo-couple means; a sensitive twocoil relay having a first fixed contact and a second contact and a movable contact normally separated from said first and second contacts and engageable with said first contact when said low voltage current is developed in one direction through one of the coils of said twocoil relay, said latter one coil being in series connection with the said thermo-couple means in said first circuit, electrically operated warning means; a second circuit provided through the other one of the coils of said relay and when closed served from a source of continuous voltage and adapted when closed to maintain said electrically operated warning means connected to said source of continuous voltage; said second circuit being normally inoperative but being completed on engagement of said movable contact with the said first contact of said relay and maintained completed independently of said relay; and electrically energised actuator operatively connected to said second contact and included in said second circuit and energised as the result of the completion of such second circuit and when energised serving to displace said second contact into a position ready for engagement by the said movable contact of the sensitive two-coil relay when the current from the thermocouple means drops to cause upon said latter engagement shorting out of the said actuator and the returning of the second contact to an idle or free position clear of the said movable contact.

4. Apparatus according to claim 3 including a condenser between said source of continuous voltage and said first contact of the two-coil relay and adapted by reason of the direction of displacement charging current therethrough relative to the said other one of the coils of said relay as to cause an implementary pressure between said movable contact and saidfirst contact of the relay upon engagement of such contacts.

5. Apparatus for giving a signal of a sudden high rate of change of temperature, eg such as occurs on the outbreak of fire at a control source, comprising thermo-couple means adapted to produce a low voltage signal consequent upon a sudden rise in temperature at said source; a first circuit including and deriving low voltage current from said thermo-couple means; a sensitive two-coil relay having a first fixed contact and a second contact and a movable contact normally separated from said first and second contacts and engageable with said first contact when said low voltage current is developed in one direction through one of the coils of said two-coil relay, said latter one coil being in series connection with the said thermo-couple means in said first circuit, electrically operated warning means; a second circuit provided through the other one of the coils of said relay and when closed served from a source of continuous voltage and adapted when closed to maintain said electrically operated warning means connected to said source of continuous voltage; said second circuit being normally inoperative but being completed on engagement of said movable contact with the said first contact of said relay and maintained completed independently of said relay; an electrically energised actuator operatively connected to said second contact and included in said second circuit and energised as the result of the completion of such second circuit and when energised serving to displace said second-contact into a position ready for engagement by the said movable contact of the sensitive two-coil relay when the current from the thermo-couple means drops to cause upon said latter engagement shorting out of the said actuator and the returning of the second contact to an idle or free position clear of the said movable contact, and a manually operable switch; a first resistor and a second resistor of higher value than the first resistor, said switch normally shorting said first resistor, said first resistor being connected across the control source and the first coil of the sensitive relay, said switch being actuable to connect the higher source of to the said first coil of the sensitive relay via said first resistor and said second resistor to introduce a test signal into the apparatus.

6. Apparatus for giving a warning when there is a sudden high rate of change in temperature, eg such as occurs at the outbreak of fire, a thermo-couple assembly to detect such form of change to produce a low EMF. signal, a very sensitive relay operable by said signal; a normally cut-out electrically operated warning appliance; a normally cut-out holding circuit served from a source of continuous voltage and adapted when closed to connect said warning appliance to said source of continuous voltage; a master relay to bring in said holding circuit and warning appliance and controlled by said very sensitive relay when such very sensitive relay is actuated by said signal; said master relay being served from said source of continuous voltage; said very sensitive relay having first and second contacts and a moving contact normally separated from said two contacts and actuated by the said low signal to engage the said first one of the contacts to bring in the said master relay to close the holding circuit and subsequently to engage the second one of said contacts to cut out said master relay and holding circuit and restore the apparatus to its normal condition; an electrically energisable actuator normally deenergised to hold said second contact out of the path of movement or" said moving contact and adapted when energised to apply displacement to said second contact into the path of free movement of said movable contact, said actuator being connectable for energising to said continuous voltage source in common with said warning appliance.

References Cited in the file of this patent UNITED STATES PATENTS 1,066,731 Jaynes July 8, 1913 1,090,412 Rennert Mar. 17, 1914 1,279,653 Cardwell Sept. 24, 1918 1,330,507 Willenbruch Feb. 10, 1920 2,589,869 Rufile Mar. 18, 1952 2,780,709 Thompson et al. Feb. 5, 1957 2,820,218 Lovegrove Ian. 14-, 1958 2,894,251 Rufi'le July 7, 1959 

